Compressor

ABSTRACT

A first tank, a main body of a compressor, an electric motor, and a second tank are combined to form a single assembly. A booster type air compressor as the single assembly including the first tank may be easily carried. The first tank at an inlet side is integrally combined to prevent a pulsation in the supplied compressed air for eliminating the drain contained in the compressed air. The air compressor, thus, is structured to discharge high compressed air from a high-pressure outlet joint formed on the second tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compressor which boosts preliminarycompressed fluid such as air so as to be stored as high compressed fluidin a tank.

2. Description of the Related Art

In a recent plant, a piping for supplying compressed air into a planthas been installed such that various pneumatic devices connected to therespective outlet joints of the piping may be operated. If thecompressed air at the pressure higher than the one supplied from thepiping in the plant is required, the compressor is connected to theoutlet joint of the piping for further boosting the preliminarilycompressed air supplied from the piping.

Japanese Unexamined Patent Application Publication No. 2007-51614discloses a booster type compressor formed of a main body driven by anelectric motor to suck air for recompression so as to discharge theresultant high compressed air, and a tank which stores the highcompressed air discharged from the main body of the compressor.

The employed booster type compressor in general has the main bodydirectly connected to the piping in the plant. As the other pluralpneumatic devices are connected to the piping in the plant, thecompressed air may cause pulsation depending on the state in the usage.The compressed air inside the piping of the plant may form drain owingto the change in the pressure or the temperature.

When the booster type compressor is installed in the piping of theplant, an inlet tank is required to be provided between the piping inthe plant and the main body of the compressor so as to prevent pulsationin the compressed air supplied and to discharge the drain.

In the aforementioned case, the space for setting the additional inlettank separately from the compressor is required, thus increasing as thecost for setting the tank and the piping. When the booster typecompressor is used in the other place, both the compressor and the inlettank have to be moved, resulting in large labor and considerable timerequired for laying out those devices.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide acompressor which may be easily installed in a small space withoutpreparing an additional inlet tank.

The present invention provides a compressor which includes a first tankconnected to an external compressed fluid source for accommodating aninflow of a low compressed fluid from the external compressed fluidsource, a main body of the compressor for sucking the low compressedfluid from the first tank so as to be compressed, and a second tank forstoring a high compressed fluid compressed by the main body of thecompressor, and for discharging the stored high compressed fluid tooutside with a high-pressure outlet joint. The first tank, the main bodyof the compressor, and the second tank are combined to form a singleassembly.

The first tank may be provided with a low-pressure outlet joint fordischarging the low compressed fluid contained in the first tank.

The first inflow pressure control valve may be provided between thecompressed fluid source and the first tank for regulating the inflow ofthe compressed fluid at a pressure in excess of a specified pressureinto the first tank.

A second inflow pressure control valve may be provided between the firsttank and the main body of the compressor for regulating the inflow ofthe compressed fluid at a pressure in excess of a specified pressurefrom the first tank to the main body.

The first tank may be provided with a relief valve which releases thecompressed fluid to outside when a pressure within the first tankexceeds a set pressure.

A path extending from the external compressed fluid source to the mainbody of the compressor is provided with a filter for eliminating dustcontained in the compressed fluid.

The first tank and the second tank have cylindrical bodies in parallelwith each other in a longitudinal direction, and are horizontallyinstalled with respect to a mount surface.

The first tank and the second tank may have cylindrical bodies inparallel with each other in a longitudinal direction, and verticallyinstalled on a mount surface.

The first tank and the second tank may be provided with a gaptherebetween. The main body of the compressor may be interposed betweenthe first tank and the second tank so as to be partially fit in the gap.

Each of the first tank and the second tank may be provided with a drainvalve for discharging a drain.

The structure may be provided with a communication pipe for allowing thefirst tank and the second tank to communicate with each other, whereinthe communication pipe is provided with a check valve which allows thecompressed fluid to flow from the first tank to the second tank butblocks an inverse flow.

The structure may be provided with an intake switching valve providedbetween the first tank and the main body, wherein the intake switchingvalve allows the main body to suck an external air upon its start-up andswitches to a state where the main body sucks the compressed fluid fromthe first tank when a pressure within the second tank reaches a setpressure.

In the structure, the single assembly formed by combining the firsttank, the main body of the compressor, and the second tank may beprovided with handgrips at both ends of cylindrical bodies of the tankssuch that the assembly is gripped.

The first tank, the main body, and the second tank may be stored in acase.

According to an embodiment of the present invention, the compressor as asingle unit may be easily carried to the other place, and set in a smallspace requiring less time and labor. The booster compressor may be setin various places for supplying the high compressed fluid.

According to an embodiment, as the first tank is provided with thelow-pressure outlet joint, the low compressed fluid stored in the firsttank may be discharged from the low-pressure outlet joint. This allowsthe single compressor to supply the high compressed fluid and the lowcompressed fluid.

According to an embodiment of the present invention, a first inflowpressure control valve for regulating an inflow of the compressed fluidat the pressure in excess of the specified pressure into the first tankis provided between the compressed fluid source and the first tank. Evenif the pressure at the side of the compressed fluid source varies, thefirst inflow pressure control valve allows the pressure within the firsttank to be suppressed within a specified pressure range. This makes itpossible to form the first tank using the inexpensive material and partsfor the low pressure specification without employing the material thatresists the high pressure, or the special parts.

According to an embodiment of the present invention, the second inflowpressure control valve for regulating the inflow of the compressed fluidat the pressure in excess of the specified pressure into the main bodyof the compressor from the first tank is provided between the first tankand the main body of the compressor. This makes it possible to preventthe compressed fluid at the pressure equal to or higher than thespecified pressure from flowing into the main body of the compressor,thus keeping the main body of the compressor from damage.

According to an embodiment of the present invention, the first tank isprovided with a relief valve which releases the compressed fluidcontained within the first tank at the pressure in excess of the setpressure to outside. This makes it possible to prevent the innerpressure within the first tank from becoming equal to or higher than thespecified pressure.

According to an embodiment of the present invention, a path extendingfrom the external compressed fluid source to the main body of thecompressor is provided with a filter for eliminating dust contained inthe compressed fluid. So the dust contained in the compressed fluidsupplied from the compressed fluid source may be eliminated by thefilter, thus preventing reduction in the life of the main body of thecompressor owing to the intake dust.

According to an embodiment of the present invention, the first and thesecond tanks have the cylindrical bodies in parallel with each other ina longitudinal direction, and are horizontally installed with respect toa mount surface, thus suppressing the height of the compressor to below.

According to an embodiment of the present invention, the first and thesecond tank have the cylindrical bodies in parallel with each other in alongitudinal direction, and installed vertically on the mount surface,thus reducing the required space for setting.

According to an embodiment of the present invention, the first and thesecond tanks are arranged having a gap therebetween, and the main bodyof the compressor is provided between the first and the second tanks soas to be partially accommodated in the gap therebetween. This makes itpossible to integrally form the compressor with low height, thusrealizing the compact structure.

According to an embodiment of the present invention, each of the firstand the second tanks is provided with a drain valve for discharging thedrain. The drain valve is opened to discharge the drain within the tank.

According to an embodiment of the present invention, a communicationpipe is provided for communicating the first and the second tanks. Thecommunication pipe is provided with a check valve which allows thecompressed fluid to flow from the first tank to the second tank butblocks the inverse flow. The low compressed fluid flowing from thecompressed fluid source to the first tank is allowed to flow into thesecond tank via the communication pipe simultaneously.

Accordingly, the pressure within the second tank may be boosted in ashort period of time. The check valve is capable of preventing the highcompressed fluid within the second tank from flowing back into the firsttank via the communication pipe.

According to an embodiment of the present invention, an intake switchingvalve is provided between the first tank and the main body of thecompressor to switch between a state where the main body of thecompressor sucks external air upon start-up of the main body, and astate where the main body sucks the compressed fluid from the first tankwhen the pressure within the second tank reaches the set pressure. Theintake switching valve allows the main body of the compressor to suckthe external air upon its start-up to reduce the resultant load.

According to an embodiment of the present invention, an assembly formedby combining the first tank, the main body of the compressor, and thesecond tank is provided with handgrips at both ends of the cylindricalbodies in the longitudinal direction. The compressor formed as thesingle assembly may be easily and safely carried to the place requiringthe high compressed fluid by gripping the handgrips.

According to an embodiment of the present invention, the first tank, themain body of the compressor and the second tank are stored in the case,thus reducing the noise during the operation as well as improving theouter appearance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a booster type air compressor according to afirst embodiment of the present invention;

FIG. 2 is a view showing a left side of the booster type air compressorshown in FIG. 1;

FIG. 3 is a circuit diagram of the booster type air compressor;

FIG. 4 is a timing chart representing the operation of the booster typeair compressor;

FIG. 5 is a front view of a booster type air compressor according to asecond embodiment of the present invention;

FIG. 6 is a front view of a booster type air compressor according to athird embodiment of the present invention;

FIG. 7 is a view showing a left side of the booster type air compressorshown in FIG. 6;

FIG. 8 is a front view of the booster type air compressor according to afourth embodiment of the present invention with a partially broken viewof the case;

FIG. 9 is a view showing a left side of the booster type air compressorshown in FIG. 8 with the partially broken view of the soundproof case;and

FIG. 10 is a circuit diagram of a booster type air compressor accordingto a modified example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A booster type air compressor will be described referring to thedrawings as a compressor according to an embodiment of the presentinvention.

FIGS. 1 to 4 show a first embodiment of the present invention. Referringto FIGS. 1 and 2, a booster type air compressor 1 according to the firstembodiment is formed by combining a first tank 2 to be described later,a main body 5 of the compressor, an electric motor 8, and a second tank9 into a single assembly.

The first tank 2 forms a lower section of the air compressor 1 forstoring compressed air at low pressure supplied from a compressed airsource 33 to be described later as a cylindrical tank with both sidessealed. The first tank 2 has the cylindrical body in parallel with thesecond tank 9, and are horizontally installed with respect to a mountsurface in the plant. Meanwhile, the first tank 2 is structured to havea sufficient capacity to absorb the pulsation of the low compressed airsupplied from the compressed air supply source 33.

As the first tank 2 stores the low compressed air (for example, thepressure of about 0.5 MPa), it is structured to have the strengthsufficient to resist the low pressure. That is, the first tank 2 may beformed using the inexpensive material which is easily processed, forexample, a thin steel plate and parts.

As shown in FIG. 2, the first tank 2 is provided with an intake joint 3and a low-pressure outlet joint 4. The intake joint 3 is connected tothe compressed air supply source 33 via a filter 14 and a first reducingvalve 15 which will be described later. The low-pressure outlet joint 4may be connected to a pneumatic device (not shown) usable at the lowpressure.

The main body 5 of the compressor sucks the low compressed air from thefirst tank 2 so as to be compressed. The main body 5 may be employed forvarious types of compressors such as rotary type and reciprocating type.In the embodiment, it is formed as a reciprocating compressor of V-typewith two-cylinder single compression mechanism. The main body 5 includescrankcases 5A each formed on the respective tanks 2 and 9, and twocompression units 5B of reciprocating type each mounted on the upperportion of the crankcase 5A. The main body 5 is linked with an electricmotor 8 via a pulley and a belt (not shown).

Inlet portions of two compression portions 5B which form the main body 5are connected to the first tank 2 via an intake pipe 6. Meanwhile,outlet portions of those two compression portions 5B are connected to aninflow joint 10 of the second tank 9.

The electric motors 8 are provided in the vicinity of the main body 5 onthe respective tanks 2 and 9, and are rotated upon power supply to drivethe main body 5.

The second tank 9 forms the lower section of the air compressor 1together with the first tank 2. The second tank 9 stores the compressedair at high pressure supplied from the main body 5, which may have acylindrical shape with both ends sealed likewise the first tank 2. Thesecond tank 9 is arranged such that the longitudinal direction of thecylindrical body is in parallel with the first tank 2, and is installedhorizontally with respect to the mount surface in the plant.

The second tank 9 stores the high compressed air (for example,approximately 1.0 MPa), and includes two inflow joints 10 and a singlehigh-pressure outlet joint 11. The two inflow joints 10 are connected tothe compression portions 5B of the main body 5 via outlet pipes 7,respectively. The high-pressure outlet joint 11 may be connected to apneumatic device (not shown) to be used at the high pressure.

Configurations of the first and the second tanks 2 and 9 will bedescribed hereinafter. In the first embodiment, the first tank 2 hassubstantially the same outer configuration as that of the second tank 9in consideration with the productivity and the balance in the externalappearance. Each of the first and the second tanks 2 and 9 may be formedto have the minimum possible volume for the purpose of making the aircompressor 1 light-in-weight and compact.

A communication pipe 12 communicates the first tank 2 with the secondtank 9, and distributes the low compressed air which has been suppliedto the first tank 2 to the second tank 9. A check valve 13 to bedescribed later is provided in an intermediate position of thecommunication pipe 12.

The check valve 13 is provided in the intermediate position of thecommunication pipe 12 for communicating the first tank 2 with the secondtank 9. The check valve 13 allows the low compressed air to flow fromthe first tank 2 to the second tank 9 via the communication pipe 12 butblocks the inverse flow of the high compressed air from the second tank9 to the first tank 2.

Various components installed in the air compressor 1 will be describedreferring to FIGS. 1 to 3.

The components of the first tank 2 will be described. The first filter14 is provided between the compressed air source 33 and the first tank 2in the plant for eliminating dust contained in the compressed fluid tobe supplied from the compressed air source 33.

The first reducing valve 15 as the first inflow pressure control valveis provided downstream of the first filter 14 between the compressed airsource 33 and the first tank 2. The first reducing valve 15 regulatesthe inflow of the compressed fluid at the pressure in excess of thespecified pressure (for example, 0.5 MPa) into the first tank 2.

A low-pressure relief valve 16 provided in the tank 2 releases thecompressed air to outside when the pressure within the first tank 2exceeds the set pressure (for example, 0.5 MPa). A drain valve 17 isprovided in the first tank 2 for discharging the drain within the firsttank 2 to outside.

A second reducing valve 18 as a second inflow pressure control valve isprovided between the first tank 2 and the main body 5, that is, at theintermediate position inside the intake pipe 6. The second reducingvalve 18 prevents the compressed air at the pressure in excess of thespecified pressure (for example, 0.5 MPa) from flowing to the main body5 from the first tank 2.

A second filter 19 is provided downstream of the second reducing valve18 at the intermediate portion inside the intake pipe 6. The secondfilter 19 eliminates dust, water content, and oil content of thecompressed air supplied to the main body 5.

Components of the second tank 9 will be described referring to FIGS. 1to 3.

A high-pressure relief valve 20 is provided on the second tank 9 forreleasing the compressed air to outside when the pressure within thesecond tank 9 exceeds the set pressure (for example, 1.0 MPa). A drainvalve 21 is provided in the second tank 9 for discharging the drainwithin the second tank 9 to outside.

A pressure switch 22 is provided on the second tank 9 for outputting adetection signal to a motor control switch 29 (described later) forcontrolling the electric motor 8. More specifically, the pressure switch22 outputs a detection signal to stop the electric motor 8 when thepressure within the second tank 9 reaches 1.0 MPa, and further outputsthe detection signal to start the electric motor 8 when the pressurewithin the second tank 9 decreases to 0.8 MPa.

A structure for reducing the load required to start the main body 5 willbe described.

An intake switching valve 23 is provided in the intake pipe 6, which isswitched to a state where the main body 5 sucks external air uponstart-up thereof, and to a state where the main body 5 sucks thecompressed air from the first tank 2 when the pressure within the secondtank 9 reaches the set pressure (for example, 0.2 MPa).

The intake switching valve 23 is formed as a three-port two-position airpilot type switching valve for supplying external air to the main body 5at a switching position (A) in a normal state. Meanwhile, upon supply ofthe pilot pressure, the valve is switched to a switching position (B)for supplying the compressed air from the first tank 2 to the main body5. The pilot portion of the intake switching valve 23 is connected tothe second tank 9 via a pilot pipe 24. An external inlet filter 25 isformed at a position where the external air is accommodated by theintake switching valve 23.

An electromagnetic switching valve 26 formed as the three-porttwo-position electromagnetic pilot type directional switching valve isprovided close to the second tank 9 on the pilot pipe 24. When the powerstate is OFF, the valve is at a switching position (C) to allow thepilot portion of the intake switching valve 23 to be opened to theatmosphere via the pilot pipe 24. Meanwhile, the electromagneticswitching valve 26 is switched to a switching position (D) when thepower state is ON for supplying the compressed air within the secondtank 9 to the intake switching valve 23 via the pilot pipe 24.

A speed control valve 27 is provided close to the intake switching valve23 of the pilot pipe 24 for reducing the flow rate of the pilot pipe 24to delay the time (timing) for the air pressure from the second tank 9to switch the intake switching valve 23.

Specifically, when the main body 5 is started, the intake switchingvalve 23 is not switched when the pressure within the second tank 9 isequal to or lower than 0.2 MPa. When the pressure within the second tank9 reaches 0.2 MPa, the intake switching valve 23 may be switched. Themain body 5 is allowed to accommodate the external air during a perioduntil the intake switching valve 23 is switched, and also to operate theelectric motor 8 at low load until the rated revolution number.

In a normal operation mode where the main body 5 is started and stoppedin accordance with pressure change within the second tank 9, thepressure within the second tank 9 is not reduced to be equal to or lowerthan 0.2 MPa. Upon start-up of the main body 5, the intake switchingvalve 23 is momentarily switched in accordance with the pressure withinthe second tank 9 (for example, at approximately 0.8 MPa), thus failingto operate the main body 5 at the low load. The speed control valve 27throttles the flow rate in the pilot pipe 24 to operate the main body 5(electric motor 8) at the low load by delaying the switching timing ofthe intake switching valve 23 by a predetermined period even when theinner pressure with the second tank 9 is equal to or higher than 0.2MPa.

An electric system for starting/stopping the motor 8 and theelectromagnetic switching valve 26 will be described referring to FIG.3.

A power switch 28 for the booster type air compressor 1 is used forstarting/stopping the electric motor 8 (main body 5), and connected to amotor control switch 29 (described later).

The motor control switch 29 is provided between the electric motor 8 anda power supply 30, and connected to the power switch 28, the pressureswitch 22 and a switching valve control switch 31 (described later). Themotor control switch 29 is used for starting/stopping the electric motor8 based on the detection signal from the pressure switch 22 or thestarting/stopping signal from the power switch 28.

The switching value control switch 31 is connected to the pilot portionof the electromagnetic switching valve 26 which is switched therebybased on the signal from the motor control switch 29.

Four wheels 32 (only two wheels are shown) are provided below the firsttank 2 and the second tank 9. Those wheels 32 allow the air compressor 1as the entire body including the first tank 2 at the inlet side to beeasily moved.

A compressed air source 33 supplies the compressed air into the plant,for example, the compressed air at the rated pressure of approximately0.5 MPa via a plant piping 34.

The compression operation of the above-structured booster type aircompressor 1 according to the first embodiment will be describedreferring to the timing chart showing in FIG. 4.

In the air compressor 1, the first tank 2 is connected to the compressedair source 33, and the pressure within the first tank 2 becomes 0.5 MPaas the supply pressure of the low compressed air. The pressure withinthe second tank 9 communicated with the first tank 2 via thecommunication pipe 12 becomes 0.5 MPa.

When the power switch 28 is turned ON in the aforementioned state, astart-up signal is input to the motor control switch 29 to drive androtate the electric motor 8 for activating the main body 5.Simultaneously the start-up signal from the motor control switch 29 isinput to the switching valve control switch 31 such that theelectromagnetic switching valve 26 is switched to the switching position(D), and the compressed air within the second tank 9 is supplied to thepilot portion of the intake switching valve 23 via the pilot pipe 24.The flow rate of the compressed air which passes through the pilot pipe24 is regulated by the speed control valve 27. So the intake switchingvalve 23 is switched from the switching position (A) to (B) with apredetermined delay time from start-up of the electric motor 8 and themain body 5, for example, in the range from 1 to 10 seconds.

The main body 5 is allowed to suck the external air upon start-up, thusreducing the starting load. As a result, the speed may immediately reachthe rated revolution number of the electric motor 8. When the intakeswitching valve 23 is switched to the switching position (B) upon elapseof a predetermined time, the main body 5 sucks the preliminarilycompressed low compressed air from the first tank 2, and furthercompresses (boosts) to allow efficient supply of the high compressed airinto the second tank 9.

Meanwhile, when the pressure within the second tank 9 reaches 1.0 MPa,the high-pressure detection signal is output from the pressure switch 22so as to be input to the motor control switch 9, thus stopping theelectric motor 8. Simultaneously, the stop signal is input from themotor control switch 29 to the switching valve control switch 31 suchthat the electromagnetic switching valve 26 returns to the switchingposition (C). The pilot pipe 24, then, is opened to the atmosphere. Thismakes it possible to allow the intake switching valve 23 to return tothe switching position (A) for sucking the external air.

When the pressure within the second tank 9 is lowered to 0.8 MPa, thelow-pressure detection signal is output from the pressure switch 22 tobe input to the motor control switch 29 for starting the electric motor8. Simultaneously, the start-up signal from the motor control switch 29is input to the switching valve control switch 31 to switch theelectromagnetic switching valve 26 to the switching position p) forsupplying the compressed air within the second tank 9 to the intakeswitching valve 23 via the pilot pipe 24. The main body 5 is operated asdescribed above to allow supply of the high compressed air to the secondtank 9.

When the power switch 28 is opened, the electric motor 8 is stopped, andthe electromagnetic switching valve 26 is switched to the switchposition (C) in response to the stop signal from the motor controlswitch 29 simultaneously. The pilot pipe 24 is then opened to theatmosphere to stop (end) the operation of the air compressor 1.

According to the first embodiment, the first tank 2, the main body 5,the electric motor 8, the second tank 9 and the like are combined into asingle assembly. Accordingly, the booster type air compressor 1 may beeasily carried as the single unit so as to be moved to the other place.

As a result, the booster type air compressor 1 may be installed in thesmall mount space with less labor and time. The work set for installingthe inlet tank, the piping work and the like may be omitted to allow thebooster type air compressor 1 to be installed in the place requiring thehigh compressed air with easy operation.

The first tank 2 connected to the plant piping 34 for supplying thecompressed air prevents pulsation of the compressed air to be supplied,and separates the drain contained in the compressed air to beeliminated. The main body 5 compresses the preliminary compressed air tobe further compressed again. As a result, the high compressed air may besupplied into the second tank 9 as well as to the pneumatic deviceconnected to the second tank 9.

The low-pressure outlet joint 4 provided in the first tank 2 is capableof discharging the low compressed air which has been stored in the firsttank 2. The high-pressure outlet joint 11 provided in the second tank 9discharges the high compressed air stored therein. The single aircompressor 1 is allowed to supply both the high compressed air and thelow compressed air which may be adapted to various types of thepneumatic devices.

The first reducing valve 15 for regulating the inflow of the compressedair at the pressure in excess of the specified pressure (0.5 MPa) to thefirst tank 2 is capable of controlling the pressure within the firsttank 2 to be within the specified pressure. This makes it possible toform the first tank 2 using the inexpensive material and the parts forlower pressure rather than the use of the material which resists thehigh pressure or the special parts.

The second reducing valve 18 for regulating the inflow of the compressedair at the pressure in excess of the specified pressure (0.5 MPa) fromthe first tank 2 the main body 5 is provided in the inlet pipe 6 forconnecting the first tank 2 and the main body 5. This may prevent thecompressed air at the pressure equal to or higher than the specifiedpressure from being supplied to the main body 5 while being kept fromthe damage and improving the reliability.

As the low-pressure relief valve 16 is provided in the first tank 2 forreleasing the compressed air to outside when the inner pressure thereofexceeds the preliminary set pressure (0.5 MPa), the pressure within thefirst tank 2 may be maintained in the safe pressure range. Likewise, thehigh-pressure relief valve 20 for releasing the compressed air tooutside when the inner pressure of the second tank 9 exceeds the setpressure (1.0 MPa), the pressure within the second tank 9 may be kept inthe safe pressure range.

The path extending from the compressed air source 33 to the main body 5is provided with the filters 14 and 19 for eliminating the dustcontained in the compressed air. The dust contained in the compressedair, thus may be eliminated, and accordingly reduction in the life ofthe main body 5 owing to the intake dust may be prevented.

The first tank 2 and the second tank 9 have the cylindrical bodies inparallel with each other in the longitudinal direction, and arehorizontally installed with respect to the mount surface of the plant.The air compressor 1 may have the height reduced resulting from thetransverse arrangement of the tanks 2 and 9.

Drains within the first tank 2 and the second tank 9 may be easilydischarged by opening the drain valve 17 for discharging the drain tooutside provided in the first tank 2 and the drain valve 21 provided inthe second tank 9.

As the first tank 2 and the second tank 9 are communicated via thecommunication pipe 12, the low compressed air which flows from thecompressed air supply source 33 to the first tank 2 is allowed to flowinto the second tank 9 in the communication pipe 12 simultaneously. Thepressure within the second tank 9 may be boosted within the shortperiod. The communication pipe 12 includes the check valve 13 whichallows the flow of the compressed air from the first tank 2 to thesecond tank 9 but blocks the inverse flow. The check valve 13 is capableof preventing the high compressed air within the second tank 9 fromreturning to the first tank 2 via the communication piping 12.

The inlet pipe 6 includes the intake switching valve 23 which isoperated to switch between a state where the main body 5 sucks theexternal air upon star-up, and a state where the main body 5 sucks thecompressed air from the first tank 2 when the pressure within the secondtank 9 reaches the set pressure. The intake switching valve 23 allowsthe main body 5 to suck the external air upon start-up to reduce thestart-up load.

A second embodiment of the booster type air compressor according to thepresent invention will be described referring to FIG. 5.

In the embodiment, the first tank and the second tank have thecylindrical bodies in parallel with each other in the longitudinaldirection, and vertically installed on the mount surface. In the secondembodiment, the same components as those in the first embodiment will bedesignated with the same reference codes with dash.

FIG. 5 shows a booster type air compressor 41 according to the secondembodiment. A first tank 42 and a second tank 43 which form the aircompressor 41 have the cylindrical bodies in parallel with each other inthe longitudinal direction, and vertically installed on the mountsurface using leg portions 42A and 43A. This makes it possible to reducethe space requiring installation of the air compressor 41.

A main body 5′ of the compressor and an electric motor 8′ are mounted ona base 44 above the first tank 42 and the second tank 43. A power switch28′ and a motor control switch 29′ are provided between the main body 5′and the electric motor 8′.

The first tank 42 is provided with an inflow joint 3′, a low-pressureoutlet joint 4′, a low-pressure relief valve 16′, and a drain valve 17′.Meanwhile, the second tank 43 is provided with a high-pressure outletjoint 11′ and a drain valve 21′. A check valve 13′ is provided on acommunication pipe 12′ which communicates the first tank 42 and thesecond tank 43.

The inlet pipe 6′ includes a second reducing valve 18′, a second filter19′, an intake switching valve 23′ and the like as well as an externalinlet filter 25′, an electromagnetic switching valve 26′, a speedcontrol valve 27′ and the like.

The above structured second embodiment provides substantially the samefunctions and effects as those derived from the first embodiment.Especially in the second embodiment, the first tank 42 and the secondtank 43 have the cylindrical bodies in parallel with each other in thelongitudinal direction, and vertically installed on the mount surface ofthe plant. The space requiring the installation may be reduced by theamount resulting from vertical arrangement of the first tank 42 and thesecond tank 43. This makes it possible to install the booster type aircompressor 41 in the narrow space.

A booster type air compressor according to a third embodiment of thepresent invention will be described referring to FIGS. 6 and 7.

In the embodiment, the first tank and the second tank are arrangedhaving a gap therebetween, and the main body of the compressor isinstalled between the first and the second tanks so as to be partiallyfit therebetween.

In the embodiment, the single assembly formed by combining the firsttank, the main body and the second tank includes handgrips at both endsof the cylindrical body in the longitudinal direction such that theassembly is gripped. The third embodiment has substantially the samestructure as that of the first embodiment. The main feature of theembodiment will only be described, and description and drawing of theother portion will be omitted.

FIG. 6 shows a booster type air compressor 51 according to a thirdembodiment. FIG. 7 shows a first tank 52 as a cylindrical body, and asecond tank 53 arranged in parallel with and apart from the first tank52. The first tank 52 and the second tank 53 are transversely arrangedhorizontally to the mount surface, and are connected with each other viaa connector member 54. A predetermined gap 55 is formed between thefirst tank 52 and the second tank 53. The gap 55 partially accommodatesa main body 62 to be described later and a lower section of the electricmotor.

An inflow joint 56 and a low-pressure reducing valve 57 are provided onthe first tank 52. A low-pressure outlet joint 58 is provided on theside of the low-pressure reducing valve 57. Meanwhile, a high-pressureoutlet joint 60 is provided on the second tank 53 via the high-pressurereducing valve 59. The first tank 52 and the second tank 53 areconnected via a communication pipe 61.

The main body 62 of the air compressor 51 and an electric motor 63integrally assembled therewith in the axial direction are combined intoa single compressor unit. The main body 62 formed as a reciprocatingcompressor mechanism of horizontal two-cylinder type is connected to thefirst tank 52 via an inlet pipe 64, and to the second tank 53 via anoutlet pipe 65.

The compressor unit formed of the main body 62 and the electric motor 63is provided between the first tank 52 and the second tank 53 as shown inFIG. 7, and the lower portion is partially accommodated in the gap 55between the tanks 52 and 53.

Two handgrips 66 are attached to the single assembly formed byintegrally combining the first tank 52, the second tank 53, and the mainbody 62. Those two handgrips 66 are positioned at both ends of thecylindrical bodies of the first tank 52 and the second tank 53, eachprotruding upward. The air compressor 51 may be moved by a user bygripping the handgrips 66.

The above structured third embodiment provides substantially the samefunctions and effects as those derived from the first embodiment.Especially in the third embodiment, the first tank 52 and the secondtank 53 are arranged having the gap 55 therebetween for partiallyaccommodating the main body 62 and the electric motor 63 therein.Accordingly, the booster type air compressor 51 may be integrally formedto become low, resulting in the compact structure.

The handgrips 66 are provided at both ends of cylindrical bodies of thefirst tank 52 and the second tank 53 in the longitudinal direction. Theair compressor 51 may be easily and safely carried to the placerequiring the high compressed air by gripping the handgrips 66.

FIGS. 8 and 9 show a booster type air compressor according to a fourthembodiment of the present invention.

The embodiment is structured to have the first tank, the main body ofthe compressor and the second tank stored in a case. As the fourthembodiment has substantially the same structure as that of the firstembodiment, the main feature will only be described, and the otherportion and the drawing will be omitted.

FIG. 8 shows a booster type air compressor according to the fourthembodiment. A first tank 72 is formed as a cylindrical body (see FIG.9), and a second tank 73 is arranged in parallel with the first tank 72at a predetermined interval. The first tank 72 and the second tank 73are transversely placed so as to be horizontal to a base 86A of the case86 as the mount surface (described later), which are connected via aconnector member 74. A predetermined gap 75 is formed between the firsttank 72 and the second tank 73 for accommodating a main body 82 of thecompressor and a lower section of an electric motor 83.

The first tank 72 is provided with an inflow joint 76 which protrudesoutward of the case 86, and a low-pressure outlet joint 78 whichprotrudes outside via a low-pressure reducing valve 77. Meanwhile, thesecond tank 73 is provided with a high-pressure outlet joint 80protruding outside via a high-pressure reducing valve 79. The first tank72 and the second tank 73 are connected via a communication pipe 81.

An electric motor 83 is integrally assembled with a main body of the aircompressor 71. The main body 82 and the electric motor 83 are combinedinto the single compressor unit. The main body 82 is formed as areciprocating compressor mechanism with one stage compression forhorizontal opposing two-cylinder type, and is connected to the firsttank 72 via an inlet pipe 84, and to the second tank 73 via an outletpipe 85.

The compressor unit formed of the main body 82 and the electric motor 83is provided between the first tank 72 and the second tank 73 as shown inFIG. 9, having the lower portion partially accommodated in the gap 75formed between the tanks 72 and 73.

A box-like soundproof case 86 forms an outer shape of the air compressor71, and has the base 86A having the lower side formed as the mountsurface for accommodating the tanks 72, 73 thereon. The soundproof case86 stores the first tank 72, the second tank 73, the main body 82, andthe electric motor 83 to block the operation sound thereof so as not tobe seen from outside.

The thus structured fourth embodiment provides substantially the sameeffects and functions as those derived from the third embodiment. In thefourth embodiment, especially the first tank 72, the second tank 73, themain body 82 and the electric motor 83 are stored in the soundproof case86 so as to reduce the level of the operation sound, and to improve theouter appearance.

In the first embodiment, the first reducing valve 15 is provided as thefirst inflow pressure control valve between the compressed air source 33and the first tank 2, and the second reducing valve 18 is provided asthe second inflow pressure control valve between the first tank 2 andthe main body 5. The present invention is not limited to theaforementioned structure but may be structured to have a first isolationvalve 91 as the first inflow pressure control valve between thecompressed air source 33 and the first tank 2, and a second isolationvalve 92 as the second inflow pressure control valve between the firsttank 2 and the main body 5. The aforementioned structure may be appliedto the other embodiments.

In the first embodiment, the intake switching valve 23 for switchingbetween a state where the main body 5 sucks air and a state where themain body 5 sucks the compressed air from the first tank 2 is formed asthe switching valve of air pilot type using the compressed air withinthe second tank 9 as the pilot pressure. However, the present inventionis not limited to the aforementioned structure. The intake switchingvalve may be formed as the electromagnetic valve which is switchablebased on the electric signal from the pressure sensor and the like inthe second tank 9.

In the first embodiment, the main body 5 is formed as the compressor oftwo cylinder reciprocating type. However, the main body may be formed asthe compressor of the single cylinder reciprocating type, the scrolltype compressor, the vane type compressor and the like. Theaforementioned structure may be applied to the other embodiments.

In the respective embodiments, the booster type air compressor 1, 41,51, or 71 is used as the compressor. However, the compressor forcompressing the fluid other than nitrogen, or the compressor forcompressing the fluid such as the cooling medium may be employed.

1. A compressor comprising: a first tank connected to an externalcompressed fluid source for accommodating an inflow of a low compressedfluid from the external compressed fluid source; a main body of thecompressor for sucking the low compressed fluid from the first tank soas to be compressed; and a second tank for storing a high compressedfluid compressed by the main body of the compressor, and for dischargingthe stored high compressed fluid to outside with a high-pressure outletjoint, wherein the first tank, the main body of the compressor, and thesecond tank are combined to form a single assembly.
 2. The compressoraccording to claim 1, wherein the first tank is provided with alow-pressure outlet joint for discharging the low compressed fluidcontained in the first tank.
 3. The compressor according to claim 1,wherein a first inflow pressure control valve is provided between thecompressed fluid source and the first tank for regulating the inflow ofthe compressed fluid at a pressure in excess of a specified pressureinto the first tank.
 4. The compressor according to claim 1, wherein asecond inflow pressure control valve is provided between the first tankand the main body of the compressor for regulating the inflow of thecompressed fluid at a pressure in excess of a specified pressure fromthe first tank to the main body of the compressor.
 5. The compressoraccording to claim 1, wherein the first tank is provided with a reliefvalve which releases the compressed fluid to outside when a pressurewithin the first tank exceeds a set pressure.
 6. The compressoraccording to claim 1, wherein a path extending from the externalcompressed fluid source to the main body of the compressor is providedwith a filter for eliminating dust contained in the compressed fluid. 7.The compressor according to claim 1, wherein the first tank and thesecond tank have cylindrical bodies in parallel with each other in alongitudinal direction, and are horizontally installed with respect to amount surface.
 8. The compressor according to claim 7, wherein the firsttank and the second tank are arranged with a gap therebetween, and themain body of the compressor is provided between the first tank and thesecond tank so as to be partially accommodated in the gap.
 9. Thecompressor according to claim 7, wherein the single assembly formed bycombining the first tank, the main body, and the second tank is providedwith handgrips at both ends of the cylindrical bodies in a longitudinaldirection for gripping the assembly.
 10. The compressor according toclaim 8, wherein the single assembly formed by combining the first tank,the main body, and the second tank is provided with handgrips at bothends of the cylindrical bodies in a longitudinal direction for grippingthe assembly.
 11. The compressor according to claim 1, wherein the firsttank and the second tank have cylindrical bodies in parallel with eachother in a longitudinal direction, and are vertically installed withrespect to a mount surface.
 12. The compressor according to claim 1,wherein each of the first tank and the second tank is provided with adrain valve for discharging a drain.
 13. The compressor according toclaim 1, further comprising: a communication pipe for allowing the firsttank and the second tank to communicate with each other, wherein thecommunication pipe is provided with a check valve which allows thecompressed fluid to flow from the first tank to the second tank butblocks an inverse flow.
 14. The compressor according to claim 1, furthercomprising an intake switching valve provided between the first tank andthe main body of the compressor, wherein the intake switching valveallows the main body to suck an external air upon its start-up andswitches to a state where the main body sucks the compressed fluid fromthe first tank when a pressure within the second tank reaches a setpressure.
 15. The compressor according to claim 1, wherein the firsttank, the main body, and the second tank are stored in a case.